Old & Slow-
No worries, Mate! (I've been watching entirely too much Steve Irwin on the telly...)
I called Remington about a week ago and discussed this with a man who used to be in the repair dept. before he moved on to another position in the company.
He said that Remington's position is that the barrels that burst, resulting in lawsuits, were the result of excessive handloads and/or barrel obstructions, which can blow up ANY shotgun. Nonetheless, Remington went to better steel, which gives me more confidence. He definitely added that older barrels are okay, though.
HOWEVER...for peace of mind, you can call Remington, and give them your serial number. They can then tell you when the gun was made, and whether you can install a new, stronger barrel.
I don't know if they want me posting their 'phone number on the Net, which would result in a lot of calls, so look for it in the index of any recent issue of, "Gun Digest" or its sister titles. Or, call the operator. The company is now in Madison, NC, and they DO have an 800 number, with links to Customer Service and other divisions.
My guess is that they'll tell you the gun is fine, as long as it's in good condition. But the call will ease your concerns, and "800" calls are free.
Remember, the M870 was introduced in 1950, and we didn't hear any of this legal stuff until...what?...the 1980's? So, the barrels can't have given too much trouble, given the enormous number of M870's sold.
Lone Star